This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-261844, filed Aug. 30, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a disk drive apparatus having a head retracting mechanism and, more particularly, to an apparatus and a method for detecting a magnetic field that is externally applied to the apparatus and controlling the performance of a head load operation in accordance with the result of the detection.
2. Description of the Related Art
A hard disk drive is known as a disk drive using a disk medium as a storage medium. In a hard disk drive, a head (magnetic head) is used to read/write data from/to the disk medium. If a data read/write operation is performed in an environment where a magnetic field is externally applied to the hard disk drive, data on the disk medium is likely to be destroyed under the influence of the externally applied magnetic field. Electronic equipment such as a personal computer installed with a hard disk drive has recently been thinned and downsized. Accordingly, the hard disk drive has become susceptible to an external magnetic field.
Jpn. Pat. Appln. KOKAI Publication No. 3-242866 discloses an electronic device with a hard disk drive, such as an electronic computer, which includes a magnetic field detector for detecting a magnetic field that is applied to the hard disk drive. The Publication refers to the possibility that data will be altered when it is read/written from/to the hard disk drive to which a magnetic field is applied. If the data is altered, programs are likely to run away. According to the technique described in the Publication (referred to as prior art hereinafter), a data read/write operation is performed for the hard disk drive only when no magnetic field is applied to the hard disk drive. When a magnetic field is applied to the hard disk drive, the performance of the data read/write operation is held by a host itself. The host therefore inquires of the magnetic field detector whether a magnetic field is applied to the hard disk drive immediately before the host performs a data read/write operation for the hard disk drive.
However, the prior art pays no attention to the problem caused when the head is located above a data area secured on a disk medium of the hard disk drive and a magnetic field is applied to the hard disk drive. In other words, the problem is that when an inductive head is used, a current flows through the head by induced noise due to the external magnetic field. If a current excited by an external magnetic field flows through the head when the head is located above a data area (data track) of the disk medium, data of the data area (data track) may be destroyed even though the host holds the data read/write operation.
In general, when a disk medium reaches a constant rotation speed at the time of startup of a hard disk drive, a head is automatically loaded above a data area of the disk medium from a head retracting mechanism such as a ramp, irrespective of the operation of a host. In this state, the host can read/write data from/to the disk medium. If, however, an external magnetic field is applied to the head when the head is loaded, it is feared that data recorded on the disk medium may be destroyed due to the current flowing through the head under the influence of the external magnetic field before the host performs the data read/write operation for the disk medium. As in the prior art described above, to check whether an external magnetic field is applied to the hard disk drive immediately before a data read/write operation is not necessarily effective in terms of preventing the destruction of data recorded on the disk medium.
The present invention has been made in consideration of the above situation and an object thereof is to detect a magnetic field externally applied when a head is loaded above a data area of a disk medium from a head retracting mechanism and prevent data recorded on the disk medium from being destroyed by inhibiting the head from being loaded in accordance with the result of the detection even though a current flows through the head due to the external magnetic field.
According to an aspect of the invention, there is provided a disk drive comprising a head retracting mechanism into which a head is retracted from a data area of a disk medium. The disk drive comprises an actuator, a magnetic field detector, head load means, and control means. The actuator supports the head and drives the head in a radial direction of the disk medium. The magnetic field detector detects an externally applied magnetic field. The head load means drives the actuator and performs a head load operation to move the head from the head retracting mechanism to the data area of the disk medium. The control means checks a result of detection obtained from the magnetic field detector while the head is retracted into the head retracting mechanism and inhibits the head load means from performing the head load operation in accordance with the result of detection.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.